The present invention relates to an improved method and kit for detecting explosives selected from nitroaromatics, organic nitrates (sometimes termed colloquially "nitroesters"), nitramines, inorganic nitrates, chlorates and bromates.
Particularly since what has become known as the Lockerbie incident, in which the undetected presence of explosive in an airplane resulted in tragic loss of life as well as material damage, an awareness of the need for rapid and reliable detection of explosives has become apparent. It is also evident that antiterrorist activity, more generally, will similarly make highly desirable, the availability of means for the ready detection of explosives. The present invention seeks to meet such needs, which are felt to an increasing extent at the present time.
An explosives detection kit marketed with the participation of the present assignees has proved highly successful commercially; see Almog. J. et al, J. Energetic Materials, 4: 159-167 (1986), who described a kit for detecting nitroaromatic, nitrate ester and nitramine explosives, the identification of inorganic nitrates being a later addition.
A "Field Spot-Test Kit for Explosives" using chemical reagents in a non-sequential procedure, as well as a portable ultraviolet lamp, has also been described (see Bayton, J. F., Los Alamos National Laboratory, N.M., USA, July 1991, NTIS publication #LA-12071-MS DE91 015321). However, this publication gives little or no indication of the sensitivity of the tests described therein. The disclosures of the above-stated literature articles are explicitly incorporated by reference herein.
In spite of the commercial success of a kit for detecting nitroaromatic, nitrate ester and nitramine explosives, based on the Almog et al model (above), this suffers from a number of drawbacks, which the present invention seeks to overcome, which drawbacks may be summarized as follows:
(1) two of the reagents are highly unstable to air and light, so that once the sealed ampoules containing them have been broken For test purposes, the kit has no reliable utility after 24 hours, and it is therefore discarded; PA1 (2) one of the reagents is used in solid form, which, because of less reliable contact than a liquid, with a sample, makes a test utilizing it less reliable than is desirable; PA1 (3) the existing kit does not detect chlorates, which are a possible ingredient of improvised explosives. PA1 (a) contacting the sample with a first reagent, which is an alkaline solution of sulfanilamide or an analogous aminoaromatic azo-dye precursor, whereby the presence of a nitroaromatic type explosive affords a distinct coloration; and in the absence of such coloration, PA1 (b) contacting the same sample, which is already in contact with the first reagent, with a second reagent containing a nitrate to nitrite ion reducing agent and a diazo-coupler which gives a highly-colored product on reaction with a diazonium compound formed by reaction of the sulfanilamide or an analogous aminoaromatic azo-dye precursor with nitrite ion, the second reagent being sufficiently strongly acidic so that it neutralizes and makes acidic a mixture thereof with an equal volume of the first reagent in contact with the suspect sample, whereby the presence of an organic nitrate or nitramine type explosive affords a distinct coloration; and in the absence of such coloration, PA1 (c) contacting the same sample, which is already in contact with the first and second reagents, with zinc powder suspended in liquid phase, whereby the presence of inorganic nitrate affords a distinct coloration; and in the absence of a distinct coloration in all of steps (a), (b) and (c), a second sample is provided From the same suspect source, and is submitted to step (d), namely: PA1 (d) contacting the second sample with an aniline salt in a homogeneous strongly acidic solution including at least one water-miscible organic solvent, whereby the presence of chlorate or bromate affords a distinct coloration. PA1 (a') the first reagent contains as solvent at least one water-miscible alcohol and at least one other water-miscible organic compound; PA1 (b') the diazo-coupler contains an aminonaphthyl moiety and the second reagent comprises aqueous oxyacid; PA1 (c') the liquid phase comprises at least one water-miscible alcohol and at least one other water-miscible organic compound; PA1 (d') the strongly acidic solution comprises an oxyacid and contains also at least one water-miscible alcohol and at least one other water-miscible organic compound. PA1 (a") the First reagent contains as solvent dimethyl sulfoxide (DMSO) and at least one alcohol selected from methyl alcohol and isopropyl alcohol; PA1 (b") the diazo-coupler is N-(1-naphthyl)ethylenediamine and the second reagent comprises aqueous phosphoric acid and a reducing agent comprising hydrazine and a thiosulfate salt; PA1 (c") the liquid phase comprises dimethyl sulfoxide (DMSO) and at least one alcohol selected from methyl alcohol and isopropyl alcohol; PA1 (d") the strongly acidic solution comprises sulfuric acid and contains also DMSO and ethanol. PA1 (i) absorbent means for sampling a suspected source selected from a suspected substance, a surface of an inanimate object and the exterior periphery of a human; PA1 (ii) alkaline solution of sulfanilamide or an analogous aminoaromatic azo-dye precursor; PA1 (iii) a solution containing a nitrate to nitrite ion reducing agent and a diazo-coupler which gives a highly-colored product on reaction with a diazonium compound formed by reaction of sulfanilamide or an analogous aminoaromatic azo-dye precursor with nitrite ion, the solution being sufficiently strongly acidic so that it neutralizes and makes acidic a mixture thereof with an equal volume of the alkaline solution; PA1 (iv) zinc powder admixed with liquid means which on shaking gives zinc powder suspended in liquid phase; PA1 (v) an aniline salt in a homogeneous strongly acidic solution including at least one water-miscible organic solvent.